Plasticité de l'inhibition spinale et symptômes douloureux chez l'animal

Neurons located in the dorsal horn of the spinal cord constitute the first relay for peripheral nociceptive messages before their transmission to supraspinal structures, such as the cortex, the main CNS area for the elaboration of pain sensations. At the spinal level, pain processing by the dorsal horn neurons is determined by a frail balance between excitatory and inhibitory controls. A large number of studies have shown that exacerbation of excitatory controls occurs during inflammatory and neuropathic pain but little is known regarding the contribution of inhibition. In this review are presented original mechanisms contributing to an aggravation of pain symptoms by reducing inhibition mediated by glycinergic and GABAergic transmissions. Apart from these spinal disinhibition processes, we also give evidence that the production of neurosteroids, synthesized locally by glia and neurons in the dorsal horn, represents a novel local antinociceptive control during inflammatory pain. In summary, spinal disinhibition plays an important role during spinal pain processing and the recent identification of these local mechanisms might be of significant importance to develop novel therapeutic strategies.